Effects of Peroxidase on Hydrogen Peroxide Reaction Rate- Davidge, Bizieff, Miles, Lowenstein

Maddy Davidge, Jonah Lowenstein, Alec Bizieff, Ethan Miles

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Hydrogen Peroxide Experimental Report

AP Biology, 2°

Miramonte High School, Orinda, CA

Abstract

In our experiment we measured the rate of oxygen gas production from the decomposition of hydrogen peroxide to determine the rate of reaction of hydrogen peroxide into oxygen gas and water and to see if a peroxidase catalyst has any effect on the reaction rate. We hypothesized that if a peroxidase acts as a catalyst for hydrogen peroxide decomposition, then the rate of change of pressure of oxygen gas produced should be highest when a peroxidase is added because the enzymes in the peroxidase will increase the rate of decomposition of hydrogen peroxide. Through our experiment, we found that the hydrogen peroxide solution with a peroxidase catalyst had a 44% faster rate of reaction than the control solution.

Intro

    Hydrogen peroxide, H2O2, is a common household substance used for a variety of tasks, such as washing clothes or disinfecting cuts. Naturally, hydrogen peroxide will spontaneously dissociate into water and oxygen gas, as shown in this equation: 2H2O2 2H2O + O2. However, the dissociation of hydrogen peroxide occurs at a slow reaction rate. In order to increase the reaction rate, we added to hydrogen peroxide a catalyst called peroxidase. A peroxidase is an enzyme, generally found in living tissue, that helps to increase the rate of decomposition of hydrogen peroxide substrates by increasing its oxidation. By knowing what causes hydrogen peroxide to decompose faster, chemical companies can create new hydrogen peroxide solutions that have a longer shelf life (Thompson). In order to see how a peroxidase will affect the decomposition rate of hydrogen peroxide, we ran an experiment measuring the pressure of the oxygen gas produced by the decomposition of hydrogen peroxide. The change in pressure of oxygen gas over time will give us the rate at which the hydrogen peroxide is dissociating. Since the reaction rate is measured in moles per minute, our experimental report group converted the change in pressure to change in moles using the Ideal Gas equation, PV=nRT. If a peroxidase acts as a catalyst for hydrogen peroxide decomposition, then the rate of change of pressure of oxygen gas produced should be highest when a peroxidase is added because the enzymes in the peroxidase will increase the rate of decomposition of hydrogen peroxide. In order to test this hypothesis, we conducted three experimental trials. One trial measured the natural rate of oxygen gas production without a catalyst. The second trial measured the rate of change of oxygen gas production with a peroxidase as a catalyst. The third trial measured the rate of change of oxygen production with a peroxidase that had denatured enzymes. Since the reaction with an active peroxidase contains the enzyme to catalyze the decomposition of hydrogen peroxide, that reaction should have a greater pressure change due to an increase in the production of oxygen gas in a given time interval than the reaction containing the denatured enzyme. This means that the experimental trial will have a higher reaction rate than the control trial.

Materials

Material	Brand/Description	Quantity
Medium Sized Apple	Yakima Fresh	1
12-inch Ruler	Navy Blue	1
Knife	Forgecraft, Serrated	1
Beaker	50 mL, Pyrex	1
Graduated Cylinder	10 mL	1
Eye Dropper	Disposable, Clear Plastic	1
Graduated Cylinder	50 mL, Mallinckrodt	1
Chemistry Sensor	Passport. Pictured in Figure 1.	1
Laptop	HP Probook	1
Microwave Oven	General Electric	1
3% Hydrogen Peroxide	Safeway Brand	31 mL
Data Studio	Computer Program. Pictured in Figure 1.	1
Eye Dropper Apparatus	Inverted, attached to  glass vial. Pictured in Figure 1.	1

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Fig. 1 shows some materials used. From left to right: Data Studio computer recording data, passport sensor, eye dropper apparatus.

Procedure

Trial 1 (Negative Control):

1. Obtain all required materials (See Materials list).
2. Check to make sure all equipment is functioning properly.
3. Plug in USB Data Sensor to computer with the Data Studio program.
4. Turn on computer, run Data Studio, create experiment with a table and graph to view collected data, set Note: Make sure Pressure is measured in atm and the measure rate in 1 Hz.
5. Attach end of tube connected to Data Sensor to eyedropper tip of beaker.
6. Measure out 10 mL of the 3% hydrogen peroxide solution with a graduated cylinder.
7. Slowly pour hydrogen peroxide into beaker, measuring 10 mL carefully.
8. Put on eyedropper cap and secure tightly to prevent the surrounding air from skewing experimental results.
9. Begin collecting data for 2 minutes by hitting the Start button on Data Studio.
10. Hit Stop to stop collecting data.
11. Empty container into a safe disposal apparatus.

Trial 2 (Denatured Apple)

1.-6. Same as Trial 1

7. Cut apple into 1cm3 cube

8. Place apple in microwave oven for 20 seconds on high power

9. Take microwaved apple cube and place it into beaker

10. Pour 10mL hydrogen peroxide into beaker

11. Put on eyedropper cap and secure tightly

12. Begin collecting data for 2 minutes by hitting the Start button on Data Studio

13. Hit Stop to stop collecting data

14. Empty container into a safe disposal apparatus

Trial 3 (Apple):

1.-6. Same as Trials 1 & 2

7.  Cut apple into 1cm3 cube

8. Place apple into container

9.Pour Hydrogen Peroxide into beaker

10. Put on eyedropper cap and secure tightly

11. Begin collecting data for 2 minutes by hitting the Start button on Data Studio

12. Hit Stop to stop collecting data

13. Empty container into a safe disposal apparatus

Results

Time (seconds)	Absolute Pressure: No Catalyst (atm)	Absolute Pressure: Apple (atm)	Absolute Pressure: Denatured Apple  (Control) (atm)
0	.980	.980	.980
10	.980	.981	.980
20	.980	.981	.981
30	.981	.982	.982
40	.982	.981	.982
50	.982	.983	.983
60	.982	.984	.983
70	.983	.985	.984
80	.984	.987	.986
90	.984	.988	.986
100	.985	.988	.987
110	.986	.991	.988
120	.986	.993	.989
Total Change in Pressure (atm)	.006	.013	.009

Fig. 2: a table of our results.

Fig. 3 demonstrates the relationship between pressure (atm) and time (s).

Fig. 4 demonstrates the trend with regards to increase in pressure (atm) vs. time (s).

    The most heavily sloped trend line in terms of atmospheres/second was found in the trial using a living apple (Fig. 4). In 120 seconds, the pressure of that system rose by .013 atmospheres (Fig. 2), whereas in the trial with the denatured apple, the pressure of the system rose by only .009 atmospheres (Fig. 2), a .004 atmosphere disparity. However, both trials using the apple as a catalyst, be it denatured or still natured, saw a greater slope than in the trial without the use of a catalyst, which saw an increase in absolute pressure of .006 atmospheres (Fig. 2).

Discussion

    The results of our experiment support our initial hypothesis, that the reaction containing the active peroxidase will produce a greater pressure change due to production of oxygen gas than the reaction containing the denatured peroxidase. Over a two-minute time interval, the experimental trial (with the active peroxidase) exhibited a pressure change of 0.013 atm, compared to 0.009 atm change in the control trial (with the denatured peroxidase). This means that the experimental trial’s pressure change was 44% greater than that of the control trial. The fact that the experimental trial had a higher change in pressure over the given time interval means that it had a faster rate of reaction, as dictated by the Ideal Gas Law, PV=nRT. Because both trials were kept in the same container with the same volume and temperature, the experimental trial that exhibited a greater pressure change (P) than the control trial also exhibited a greater change in the number of moles of gas (n), which means that this trial had a faster reaction rate. However, the control trial also exhibited a 33% greater pressure change than the trial with only hydrogen peroxide. This is most likely due to the fact that, when we cooked the apple for the negative control in the microwave, not all of its peroxidase denatured, meaning that its pressure change was greater than pure hydrogen peroxide but still lower than that of the experimental trial.

One potential source for error in this experiment is the fact that our inverted dropper may have contained a leak, which would not have allowed for an accurate measurement of pressure. This could have been averted if we examined the dropper thoroughly before beginning our experiment. Another source of error is, because the distribution of peroxidase may not be perfectly even throughout the apple, one piece of apple may have contained more peroxidase than another piece, meaning that the initial concentration of peroxidase in each trial may have been slightly different, contributing to a skewed measurement of reaction rate. More accurate results could be obtained by performing multiple trials.

To get more accurate results, perhaps we could have let the reactions progress for more than two minutes. This would lead to a slightly more accurate measurement of pressure change over time and therefore reaction rate.

Citation:

Thompson, Gerard M. "What Is a Peroxidase?" WiseGEEK. Make, 23 July 2008. Web. 20 Oct. 2013.